Why aren't thyroid transplants available for people who've had to undergo thyroidectomies due to cancer?

We Don't need them: Because we have a simple replacement medicine(thyroxine), we do not need an organ transplant; organi transplant is a major undertaking. Besides finding a donor(which is a huge probelm) patients who do receive transplants have to be kept on immune suppressive medicines for a long time. That itself is a risky preposition..But it is essential in order to keep the transplanted organ functional.